THEORY:
This is because the character is still trying to find a way to continue staying diagonal from the target. It might just be a targeting issue but I don't think its something to worry about. I've seen a very similar scenario when you're at say Lizard Chosens and the special areas cause you to stay within a perimeter but next thing you know you're stuck in the corner of the cave with 3 Lizard Chosens bashing you. So basically the cave wall is against your back and the 3 Chosens have you trapped, there's nothing your character can do yet since the targeting is set to 3-4SQM diagonal, it still try to find a path to move away from those Chosens. Like I said though, I don't see this being an issue and its definitely not detectable.. rubber banding, or "banding" is in a lot of games. It can be caused from several things, take for example you go out manual hunting and you just start trying to talk face first into a dragon nonstop for 30 seconds. Doesn't mean you're botting, just means your son has his fingers on your arrow keys (happened to me plenty in the past). Its just Tibia's "bounce-back" or whatever you want to call it, the bot is only trying to find a way to stay diagonal, I think. Its been seen before in other bots in the past as well.
DarkstaR might clarify/confirm this and could probably write it out easier.